Self-oscillating switching regulator

1. A switching regulator connectable to a power supply having a DC voltage, the switching regulator comprising: a first node connectable to the power supply; a feedback node; an output node; a ground node; a power switch coupled between the first node and the output node and having a power switch control gate; an output voltage feedback circuit coupled between the output node and the feedback node, and to ground node; and a self-oscillating power switch control circuit coupled to the first node, the ground node, the feedback node, and to the power switch control gate, wherein the power switch control circuit includes a voltage reference circuit which provides a desired reference voltage, wherein the power switch control circuit compares a feedback voltage at the feedback node to the desired reference voltage, provides a first control voltage to the power switch control gate when the desired reference voltage exceeds the feedback node voltage to turn on the power switch to thereby raise the output node voltage to a desired level, and provides a second control voltage to the power switch control gate when the feedback node voltage exceeds the desired reference voltage to turn off the power switch to thereby lower the output node voltage to a desired level.

2. The switching regulator of claim 1 wherein an output filter circuit is coupled between the power switch and the output. node.

3. The switching regulator of claim 1 , wherein the voltage reference circuit comprises: a first temperature-compensated voltage reference diode having an anode and a cathode; a constant current diode coupled between the first node and the cathode of the first temperature-compensated voltage reference diode; a second temperature-compensated voltage reference diode having a cathode coupled to the anode of the first temperature-compensated voltage reference diode, and having an anode; and a resistor having a first terminal coupled to the anode of the second temperature-compensated voltage reference diode and a second terminal coupled to the ground node.

4. The switching regulator of claim 3 , wherein the voltage reference circuit further comprises a capacitor is coupled between the cathode of the first temperature-compensated voltage reference diode and the anode of the second temperature-compensated voltage reference diode to reduce in-rush current.

5. The switching regulator of claim 1 , wherein the self-oscillating power switch control circuit includes a comparator circuit to compare the desired reference voltage to the feedback . voltage.

6. The switching regulator of claim 1 , wherein the self-oscillating power switch control circuit includes a power switch biasing circuit which provides the first control voltage and the second control voltage to turn the power switch on and off.

7. The switching regulator of claim 6 , wherein the comparator circuit comprises: a first transistor with a gate coupled to a reference voltage node, a drain coupled to the power switch biasing circuit, and a source; a second transistor with a gate coupled to an output voltage reference node, a drain coupled to the power switch biasing circuit, and a source; and a resistor with a first terminal coupled to both the source of the first n-channel transistor and to the source of the second n-channel transistor, and a second terminal coupled to the ground node.

8. The comparator circuit of claim 7 , wherein the first transistor is an n-channel transistor and the second transistor is an n-channel transistor.

9. The switching regulator of claim 6 , wherein the power switch biasing circuit comprises: a first transistor having a gate coupled to both the drain of the first transistor in the comparator circuit and to a first terminal of a first resistor whose second terminal is coupled to the input node, a source coupled to a first terminal of a resistor whose second terminal is coupled to the power switch control gate, and a drain coupled to the anode of the second temperature compensated voltage reference diode in the voltage reference circuit; a second transistor with a source coupled to the input node, a drain connected to the power switch control gate, and a control gate; a second resistor with a first terminal coupled to the input node, and a second terminal coupled to the gate of the second transistor; a third resistor with a first terminal coupled to the gate of the second transistor, and a second terminal coupled to the drain of the second transistor in the comparator circuit; and a fourth resistor with a first terminal coupled to the input node, and a second terminal coupled to the power switch control gate.

10. The biasing circuit of claim 9 , wherein the first transistor is a p-channel transistor and the second transistor is a p-channel transistor.

11. A self-oscillating power switch control circuit connectable to a power supply having a DC voltage and to a power switch having a source coupled to the power supply, a drain which provides an output voltage, and a control gate, the power switch control circuit comprising: a voltage reference circuit receiving the DC voltage from the power supply and providing a desired reference voltage; a comparator circuit receiving the desired reference voltage and a feedback voltage representative of the power switch output voltage, providing a comparator output signal having a first comparator output voltage level when the desired reference voltage exceeds the feedbacks voltage and a second comparator output voltage level when the feedback voltage exceeds the desired reference voltage. a biasing circuit receiving the comparator output signal, providing a first control voltage to the power switch control gate in response to the comparator output signal being at the first comparator output voltage level to turn on the power switch to thereby raise the power switch output voltage, and providing a second control voltage to the power switch control gate in response to the comparator output signal being at the second comparator output voltage level to turn off the power switch to thereby lower the power switch output voltage.

12. The power switch control circuit of claim 11 , wherein the biasing circuit includes a transistor coupled to the power switch that turns on in response to the comparator output signal being at the first comparator output voltage level.

13. The power switch control circuit of claim 12 , wherein the voltage reference circuit slightly increases the desired reference voltage in response to the transistor being turned on.

14. The power switch control circuit of claim 11 , wherein the voltage reference circuit comprises: a first temperature-compensated voltage reference diode having an anode and a cathode; a constant current diode coupled between the first node and the cathode of the first temperature-compensated voltage reference diode; a second temperature-compensated voltage reference diode having a cathode coupled to the anode of the first temperature-compensated voltage reference diode, and having an anode; and a resistor having a first terminal coupled to the anode of the second temperature-compensated voltage reference diode and a second terminal coupled to the ground node.

15. The power switch control circuit of claim 14 , wherein the voltage reference circuit further comprises a capacitor is coupled between the cathode of the first temperature-compensated voltage reference diode and the anode of the second temperature-compensated voltage reference diode to reduce in-rush current.

16. The power switch control circuit of claim 11 , wherein the comparator circuit comprises: a first transistor with a gate coupled to a reference voltage node, a drain coupled to the power switch biasing circuit, and a source; a second transistor with a gate coupled to an output voltage reference node, a drain coupled to the power switch biasing circuit, and a source; and a resistor with a first terminal coupled to both the source of the first n-channel transistor and to the source of the second n-channel transistor, and a second terminal coupled to the ground node.

17. The power switch control circuit of claim 11 , wherein the power switch biasing circuit comprises: a first transistor having a gate coupled to both the drain of the first transistor in the comparator circuit and to a first terminal of a first resistor whose second terminal is coupled to the input node, a source coupled to a first terminal of a resistor whose second terminal is coupled to the power switch control gate, and a drain coupled to the anode of the second temperature compensated voltage reference diode in the voltage reference circuit; a second transistor with a source coupled to the input node, a drain connected to the power switch control gate, and a control gate; a second resistor with a first terminal coupled to the-input node, and a second terminal coupled to the gate of the second transistor; a third resistor with a first terminal coupled to the gate of the second transistor, and a second terminal coupled to the drain of the second transistor in the comparator circuit; and a fourth resistor with a first terminal coupled to the input node, and a second terminal aim coupled to the power switch control gate.

18. A method of providing a desired second DC voltage level from a power supply having a first DC voltage level , the method comprising: receiving the first DC voltage level from the power supply; comparing the first DC voltage level from the power supply to the desired second DC voltage level; providing a first control voltage level to a power switch control gate, to cause the power switch to turn on if the first DC voltage level is less than or equal to the desired second DC voltage level to thereby provide the first DC voltage level at an output node; and alternately providing a first control voltage level and a second control voltage level to the power switch control gate to cause the power switch to turn on and off if the first DC voltage level is greater than the desired second DC voltage, thereby turning the power switch on and off at an appropriate switching frequency to thereby provide the desired second DC voltage level.

19. The method of claim 18 , wherein the desired second DC voltage level is based on a desired reference voltage.

20. The method of claim 18 , further comprising: providing a first comparator output voltage level when the DC reference voltage level exceeds the DC feedback voltage level, and a second comparator output voltage level when the DC feedback voltage level exceeds the DC reference voltage level.

21. The method of claim 18 , further comprising providing a first biasing circuit output voltage level when the DC reference voltage exceeds the DC feedback voltage, and providing a second biasing circuit output voltage level when the DC feedback voltage exceeds the DC reference voltage.

22. A power source comprising: a power supply having a DC voltage; and a switching regulator coupled to the power supply, the switching regulator comprising: a first node connectable to the power supply; a feedback node; an output node; a ground node; a power switch coupled between the first node and the output node and having a power switch control gate; an output voltage feedback circuit coupled between the output node and the feedback node, and to ground node; and a self-oscillating power switch control circuit coupled to the first node, the ground node, the feedback node, and to the power switch control gate, wherein the power switch control circuit includes a voltage reference circuit which provides a desired reference voltage, wherein the power switch control circuit compares a feedback voltage at the feedback node to the desired reference voltage, provides a first control voltage to the power switch control gate when the desired reference voltage exceeds the feedback node voltage to turn on the power switch to thereby raise the output node voltage to a desired level, and provides a second control voltage to the power switch control gate when the feedback node voltage exceeds the desired reference voltage to turn off the power switch to thereby lower the output node voltage to a desired level.